NOTE: As their name suggests hints are not exactly Dead Space 2 cheats, and are usually just simple (but very useful) tips on how you can unlock secret level, features, find hidden areas and such. Hopefully these will make playing Dead Space 2 even more entertaining.

Hardcore Mode
Beat the game under any difficulty and you will unlock Hardcore Mode. In hardcore mode, you only get to save 3 times in the entire campaign on this difficulty and ammo/health packs are so scarce and rare. Plus if you die, you start at the last save point, not checkpoint.

Riot Suit
Logging into your same EA account through the Dead Space iOS game will unlock the Riot Suit. It grants a weapon bonus to the Contact Beam for 10% extra damage and 25 inventory slots and 25% armor.

Riot Suit: Log into your same EA account through the Dead Space iOS

Trophies
...And Stay Down (Bronze): Kill 25 crawling enemies with Stomp (single player only)
Bouncing Betty (Bronze): Kill a Cyst by catching its Mine and throwing it back
Brute Juke (Bronze): Kill a Brute without taking damage
C-Section (Bronze): Knock down an enemy with Contact Beam Alt-Fire then kill it with Primary Fire before it stands up
Clean Cut (Bronze): Sever all three tentacles of a Lurker with one Line Gun Primary Fire shot (single player only)
Clever Girls (Bronze): Survive your first encounter with Stalkers
Collect Peng (Silver): Find the Peng treasure
Cross your Heart, Hope to Die (Bronze): Survive the Eye Poke Machine
Derailed (Bronze): Survive the Train SequenceElevator Action (Bronze): Knock off every Tripod during the Elevator Sequence
Epic Dismemberment (Silver): Dismember 2,500 Necromorph Limbs (single player only)
First Aid (Bronze): Use Quick Heal ten times (single player only)
Frozen in Time (Bronze): Kill 50 Necromorphs while they are in Stasis (single player only)
Fully Loaded (Bronze): Simultaneously have four completely upgraded weapons
Fully Outfitted (Bronze): Upgrade your RIG and Stasis completely
Going for Distance (Bronze): Impale an enemy and make him fly through the air for 17 meters - it must stick to the surface
Hard to the Core (Gold): Complete the game on Hard Core setting
Hornet's Nest (Bronze): Destroy the Tripod Nest
It's a Trap! (Bronze): Kill 20 enemies with Detonator Mines in a deployed state
Knock Knock (Bronze): Complete the Drill Ride
Lawnmower Man (Bronze): Kill 4 enemies with the same Ripper blade
Lightspeed de Milo (Bronze): Dismember the Lightspeed Boy Statue
Looking good (Bronze): Purchase the Advanced Suit
Made Us Whole (Bronze): Complete the game on any difficulty setting
Mission Impossible (Gold): Complete the game on Zealot setting
My Boom Stick (Bronze): Kill 6 enemies at once with Line Gun's Alt-Fire (single player only)
Necro Flamb' (Bronze): Kill 50 enemies using the Flamethrower
One Small Step (Bronze): Get through the first Zero-G area
Operation! (Bronze): Snare the Shard with the Ishimura
Patient on the Loose (Bronze): Get your first Suit
Peek a Boo! (Bronze): Kill a Stalker with the Seeker Rifle while in Zoom Mode
Picking favorites (Bronze): Upgrade 1 Weapon completely
Powered Up (Bronze): Complete the Solar Array Puzzle
Romper Stomper (Bronze): Stomp 10 Containers
Shock Therapy (Bronze): Impale an enemy with the Javelin Gun and use its Alt-Fire to shock 3 others (single player only)
Shoot the Limbs! (Bronze): Dismember 25 Necromorph Limbs (single player only)
Shut Down (Bronze): Defeat the AI
Skewered in Space (Bronze): Impale an enemy into a Decompression Window to cause it to blow out
Taste of your own Medicine (Bronze): TK Impale a live Slasher to a surface using a Slasher's arm - it must stick to the surface
The Electrician (Silver): Collect 10 Semiconductors
The Engineer (Silver): Collect 10 Schematics
The Final Frontier (Platinum): Earn all Trophies in Dead Space 2
The Final Sacrifice (Bronze): Destroy the Marker
The Fugitive (Gold): Escape the Facility
The Graduate (Bronze): Win the fight at the School
The Librarian (Bronze): Collect 100 logs
The Nanny (Bronze): Kill 30 Crawlers without detonating them
The Sampler Platter (Bronze): Kill a Necromorph with every Weapon in the game (single player only).
Think Fast (Bronze): Kill 30 Necromorphs with Kinesis objects
Torment Me No More (Bronze): Kill the Tormentor
Vacuum Cleaner (Bronze): Decompress 20 Necromorphs without getting sucked out yourself

Severed Trophies
Grind House (Bronze): Severed: In the grinder room, cause an enemy to die in the grinders
King of the Hill (Bronze): Severed: Defend the quarry platform until the door unlocks
Peng Me Again (Bronze): Severed: Find the Peng treasure in Severed
Remember the Alamo (Bronze): Severed: Kill 16 or more enemies in the final last stand combat sequence
Ship Shape (Silver): Severed: Take out the gunship within 30 seconds
The Betrayal (Silver): Severed: Complete Chapter 1
The Sacrifice (Silver): Severed: Complete Chapter 2
The Veteran (Silver): Severed: Complete on Zealot difficulty

List of Online Unlockables
Through the online career you unlock these itmes:

Refurbished Plasma Cutter
Start the game with save data from the original Dead Space on your console to unlock the Refurbished Plasma Cutter. It is only aesthetically different from the regular Plasma Cutter, designed more to look like the version found in the original Dead Space.

Refurbished Plasma Cutter: Start game with save data from Dead Space on your console, then pick it up at the first store.

Infinite Ammo Hand Cannon
If you beat the game in hardcore mode and upgraded the plasma pistol you should unlock the infinite ammo one hit kill hand cannon located in your first shop. Bang Bang! Pew Pew!

Multiplayer Skins
Complete the corresponding challenges to unlock the following skins for your human suit

Special Suits
After finishing the game, you get two suits that gaves you 25% more resistance to any hit and if you have an old Dead Space save file you get the original Plasma Cutter wich cost 0 credist and can be found on any store at any time.

Arctic Security Suit: Beat the game on Zealot difficulty to unlock at Store
Elite Advanced Suit: Schematic found in New Game + in Chapter 11 when the yellow lift reaches the top turn around and it is on the ledge between elevator and wall
Elite Engineer Suit: Schematic found in New Game + during Chapter 2, just before the first short outer space section.
Elite Security Suit: Schematic found in New Game + in Chapter 9 after you exit the tram, search over the railing.
Elite Vintage Suit: Schematic found in New Game + in Chapter 6 in the area you fight the tank before the end of the chapter.
Soldier Suit: Beat the game on Hardcore Mode to unlock at Store